Something I find really funny is how quickly Aquillon always beats Argel Tal. Like yes, custodes are stronger than space marines but not by that much, normally. For context, they’re generally as much stronger than Astartes as Astartes are to humans, according to their Codex, but with more internal variance because custodes generally have the most internal variance (Valdor fought Alpharius on pretty equal terms in Alpharius’ Primarch novel, even if Alpharius tried to count that as his win bc “Valdor wore armor and I didn’t!!!1!1!1!!2!1!”).
In A Thousand Sons, a sister of silence (unaugmented human) kept in a fight really long against Phosis T’Kar. The Eversor and Koyne, who, tbf, are enhanced, took out a SoH together. Ofc, sometimes Astartes win pretty decisively against custodes as well (The Outcast Dead), and five Astartes can take a custodes (Garro), same way five humans can also sometimes take down an entire squad of space marines (Pandorax, tho tbf those were catachans) because at the end of the day we’re all reliant on the roll of the dice.
But Argel Tal consistently and solely losing against Aquillon in a single stroke means either that Aquillon was particularly gifted (which tbf, he’s Amon Tauromachian’s kid, so maybe), or that Argel Tal is just. Really really bad.